Apparatus for mixing concrete



June 15, 1937. p w 2,083,767

APPARATUS FOR MIXING CONCRETE Filed March 13, 1929 4 Sheets-Sheet 1 WWWJune 15, 1937. w YET-r 2,083,767

APPARATUS FOR MIXING CONCRETE Filed March 13, 1929 4 Sheets-Sheet 2 V N)/%//EN7'UR x [WW June 15, 1937. P. w. YETT APPARATUS FOR MIXING CONCRETEF$led March 15, 1929 4 Sheets-Sheet 4 mZON UTZXZZ 7:464

Na E Patented June 15, 1937 UNITED STATES PATENT OFFICE APPARATUS FORmxme concurs Porter .w. Yett, Portland, Oreg.

Application March 13, 1929, Serial No. 346,570

12 Claims.

This invention relates generally to the art of mixing concrete, andparticularly to the mixing of concrete in transit.

The main object of this invention is to provide a special form of mixingapparatus whereby concrete can be thoroughly and uniformly mixedthroughout the entire mass of a batch, with the employment of only theminimum amount of water consistent with the production of the highestgrade of concrete.

The second object is to produce a mixer whose diameter is small withrelation to its length for mounting on a motor truck in which the shapeof the mixing cylinder will not interfere with $5 the thorough mixing ofthe aggregate.

The third object is to produce a concrete mixer in which the materialsmay be thoroughly mixed in transmit without particular regard as to themanner in which the materials are inserted into the mixer. I

The fourth object is to provide a mixing cylinder'in which the flightsare so arranged as to secure a number of reversals in direction oftravel with relation to the axis of the cylinder as the cylinder isrotated.

The fifth object is to provide a concrete mixing and transportingmachine, having a wide range of speed ratios at which the mixing drummay be driven. I accomplish these results in the manner set forth in thefollowing specification as illustrated in the accompanying drawings, inwhich:

Figure 1 is a plan view of the truck with the mixer removed. Figure 2 isa side elevation.

Figure 3 is a plan view. Figure 4 is a section taken along the line 4-4in Figure 2. Figure 5 is a section taken along the line 5-5 in Figure 2.Figure 6 is a section taken along the line 3-5 in Figure 2. Figure 7 isa section taken.

along the line I--1 in Figure 2. Figure 8 is a somewhat distorteddevelopment of the interior of the mixer showing the mixing flights.Figure 9 is a longitudinal section through one form of waterdistributing pipe. Figure 10 is a view 5 through a modified form ofwater distributing pipe. Figure 11 is a fragmentary side elevationshowing an alternative form of water supplying device. Figure 12 is asection taken along the line l2--l2 in Figure '11. Figure 13 is avertical 50 longitudinal section through the mixing cylinder.

Similar numbers of reference refer to similar parts throughout theseveral views.

Referring in detail to the drawings, there is shown a truck chassis l5carrying the usual cab 56 I9 and hydraulic drum hoist I'I mounted on therunning gear l8. On the chassis I5 is mounted a mixer frame I9 which ishinged on the brackets 20 which are secured on the chassis l5. 0n theforward ends of the mixer frame I 9 are the downtumed arms 2| to whichare attached the cables 22 of the hoist II. On the mixer frame l9 aremounted the circular tracks 23 within which is rotatably mounted acylindrical mixing drum 24 whose end 25 converges toward the cab l3 andis completely closed by a cap 26; whereas the end 21 converges towardthe charging mouth 28 through which materials are inserted by aconvenient chute 29, or through which the mixed concrete may bedischarged at the point of delivery.

Rotation is imparted to the drum 24 through the gear 30 and its pinion30-A on the shaft 3| which is driven by a pair of bevel gears 32 fromthe shaft 33, which is on the hinged axis of the frame l9. Motion issupplied to the shaft 33 by the bevel gears 34 through the shaft 35which passes through a secondary transmission 36 which is interposedbetween the usual transmission 31 and the gears 34.

Passing through the axis of the mixing drum 24 is a water supply pipe 38to which water is supplied from an overhead tank 39 through the piping49 under the control of a valve 4|. The tank 39 is closed and is capableof withstanding several atmospheres of pressure delivered theretothrough the pipe 42 from a reservoir 43.

In the top of the tank 39 is provided a filler cap 44 which preferablyincludes an air check valve 45 which will permit water to flow from thetank 39 after the supply of air from the reservoir 43 is exhausted. Inother words, it prevents the water in the tank 39 from being trappedtherein after the air pressure in the tank falls below that of thesurrounding atmosphere.

It is preferable to subdivide the tank 39, one side of which forms anauxiliary or flushing tank used in washing out the mixer after thematerials are discharged therefrom.

It is desirable to support the water pipe 38 by means of a spider 46 andto so reduce its diameter and space the holes 41 therein, as well aslimit their dimension, that there will be a uniform distribution ofwater along the entire length of the mixer to prevent lumping. In actualpractice the pipe 38 is either formed of a number of reducing sections(as shown in Figure 9) or as a tapering pipe 38A having holes 4IA (asshown in Figure 10).

Turning now to the interior of the drum 24 (as shown in Figure 8) as adevelopment which,

for the purpose of clarifying the explanation, is somewhat distorted andshown as a true cylinder rather than one having its ends converging, asis actually the case.

It will be noted that the charging end 2T is provided with a pluralityof' inclined charging flights 48 and one return bucket flight 49, whilethe end 25 is provided with a plurality of return flights 50 and onereturn bucket flight 5|. It will be noted that the flights 48 and 50slope in opposite directions.

Within the cylindrical portion of the drum 24 and closest the flights 48are the first mixing flights 52 which slope in the same direction as dothe flights 48. Near the flights 50 are the second mixing flights 53, 54and 55 which slope in the same direction as do the flights 50. Theflight 54 differs from the flights 53 and 55 only in the distance itextends toward the center of the cylinder. Across the middle of thecylinder are formed the tumbling flights 56 which overlap the flrst andsecond mixing flights.

The rotation; of the drum 24 is as indicated by the arrow 51 in Figures4 to 8 inclusive.

Referring, now specifically to Figure 8 there is shown, by means of thedotted lines 58, the various paths which a given quantity of aggregatesmay "follow during the mixing operation. It will be noted that as theyfall upon the charging flights 48 they are carried forward, some of themfalling into the bucket flight 49, some on the flights 52 and some onthe tumbling flights 56. Those falling on the flights 48 and 52 arenaturally advanced along the cylinder, while those falling upon thetumbling flights 56 may go backwardly or forwardly or be carried to thetop of the cylinder, from which point they are dropped to the bottom ofthe cylinder, or on some intervening flight. Those portions falling uponthe flights 53, 54 or 55 will be carried backwardly to the center of themixer where they are again picked up by the tumbling flights 56 andthrown downwardly. Those portions falling upon the carry-over flight 59,which slopes oppositely to the return flights 50, will be carried overto the extreme front end 25 of the mixing drum 24, after which they passaround the end and sides of the carry-over flight 59 and then fall uponthe flights 50, which start them backwardly toward the center of themixer.

It will be noted that the flights 48, 49, 50 and Si extend to the innersurface of the mixer; whereas the flights 52, 53, 54, 55 and 55 arespaced therefrom, as better shown in Figures 4 to '7.

While it will be possible to secure backward and forward travel of theaggregate within the mixer by the use of flights other than thoseillustrated, the arrangement employed herein possesses numerousadvantages which make the use thereof desirable.

It can be seen by a study of Figures 4 to 8 inclusive that the materialsalong' the mixer are given not only a thorough mixing with relation tothe materials near by, but also with relation to all of the other partsdisposed along the length of the mixing cylinder.

It must be understood that in charging these machines it is preferableto provide an inclined runway in which the rear end of the machine willbe uppermost, which greatly assists the distribution of the aggregatesalong the entire length of the cylinder, and of course when the mixer isdischarged the cylinder is inclined in the opposite direction by meansof the hydraulic hoist H, as is well understood. In the draw ng t p sion of the cylinder is shown as horizontal, which is the normal operatingposition, or the position of the cylinder in transit during which timethe mixing is taking place.

Now bearing in mind the desirability of thoroughly dry mixing theaggregates, then moistening same with the minimum amount of waterconsistent with the formation of first class concrete, and theimportance of then delivering concrete to the molds as soon as possibleafter it is moistened, it can readily be appreciated why it isadvantageous to mix the concrete in transit. Experience has shown thatthe best type of mixer for this purpose is a drum of relatively greatlength and small diameter and conforming somewhat to the chassis of thetruck on which it is mounted.

The use of this type of drum causes several problems to arise, flrst thediiflculty of uniformly distributing the batch along the length of thecylinder and then the dimculty of thoroughly dry mixing every particleof material in the'batch with relation to every other particle ofmaterial in the batch, and lastly the difllculty of wet mixing the batchwithout the use of an objectionable amount of water. Should largevolumes of water come in contact with the neat cement it would formlarge lumps instead of a uniform paste, which in existing typesof-machines requires additional apparatus to again break up these lumps.

With the old style drum of a large diameter and short length theaggregates could be deposited within the drum in any fashion desired andsecure fairly uniform mixing throughout the batch, owing to the factthat it is largely a tumbling operation in which little or nolongitudinal travel of the material is necessary with relation to themixing drum, but with the long small diameter drum it is desirable notonly to charge the drum in a fairly uniform manner but that thematerials themselves be moved backwardly and forwardly along the drum,as well as tumble in the ordinary fashion, in order that the promotionof ingredients in the batch and the state of saturation thereof beabsolutely uniform throughout the entire length of the mixing drum toobtain a creamy mortar without lumps.

Furthermore, should the liquid be added to the mix at one point andreliance placed upon the further mixing action of the drum to distributethe moisture in the mix it would be found that the portion of the mixwhich is over-saturated will mix with the remainder of the batch withgreat difliculty and will form in large lumps if the moisture is notuniformly supplied along the length of the cylinder.

For the purpose of insuring this uniform distribution of water andpreventing against stoppage of the outlets therefor, there is provided ameans for supplying pressure to the water tank, as above described,which will be sufllcient to dislodge any obstructions in the water atthe openings 41, after which the water can flow therefrom in asuitablemanner by gravity alone.

Turning to Figure 11 it will be seen that there is shown a pump 60 whichmay be driven by the bevel gears 6| through the shafting 62 which, inturn, is driven from the pinion 30A. Obviously, any other means forproviding an additional head for the water supply could be used withoutdeparting from the spirit of this invention.

Attention is also drawn to the fact that by the introduction of asecondary transmission 36 which can be used in conjunction with the maintransmission, a wide range of speeds can be obtained from which theoperator can select the one best adapted for the purpose, at the sametime permitting the engine to run at the desired speed for driving thetruck in transit.

The outstanding feature, of course, is the drum itself; whose rotationcauses its flights to carry the inserted charge first toward theopposite end of the cylinder and then backward toward the front thereofin repeated successions, not in a steady stream but one which isconstantly being diverged (as illustrated in Figure 8) for the purposeof securing an absolutely uniform mix along the entire length of thecylinder.

Attention is drawn to my copending application, Serial Number 313,014covering an apparatus for charging this mixture satisfactorily.

Attempts have been made to supply water to portable mixing machines intransit by gravity 20 from an overhead tank. This, however, did not workout satisfactorily unless the mixer was in a horizontal position whenthe water was being discharged into the aggregates. If it sloped in onedirection or the other the distribution of water would be unequalcausing one end of the cylinder to receive too much water and the otherend not enough, making it diflicult to fully distribute the moisture,especially on short hauls where the mixing time was limited.

30 I claim:

1. A mixing cylinder having one end of same closed and the other endopen for charging purposes, a plurality of charging flights within saidcylinder adjacent to said open end adapted to draw materials into saidcylinder, a plurality of first mixing flights sloping in the samedirection as do said charging flights, a plurality of second mixingflights sloping in the opposite direction to said flrst mixing flights,tumbling flights between said first and second mixing flights, andreturn flights at the closed end of said cylinder sloping in thedirection of said second mixin flights.

2. A cylinder for mixing concrete having a normally horizontal axis,means for inclining said axis away-from the horizontal, said cylinderhaving an open charging end whose opposite end is closed, a plurality ofcharging flights mounted within said charging end adapted to movematerials toward the closed end of said cylinder, a plurality of returnflights at the closed end of said cylinder adapted to move materialstoward the charging end there0f,= a plurality of first mixing flightsadjacent said charging flights for moving materials in the samedirection as do said charging flights, a plurality of second mixingflights adjacent said return flights adapted to move materials towardthe charging end of the cylinder, a plurality of tumbling flightsparallel to the axis of the cylinder and mounted between said flrst andsecond mentioned mixing flights, and a carry-over flight extending fromthe closed end of said cylinder to said tumbling flights whereby aportion of the materials falling from said tumbling flights shall becarried directly to the closed end of said cylinder.

3. A concrete mixing drum consisting of a cylinder whose length is inexcess of its diameter having tapering ends formed thereon one of whichis open and the other of which is closed, the open end having aplurality of charging flights mounted thereon close to its innersurface, the closed end having a plurality of return flights mountedthereon also close to its inner surface adapted to move materials in theopposite direction to said charging flights, a carry-over flightextending from said closed end to the middle of the cylinder adapted toconvey materials toward said closed end, opposed first and second mixingflights within said cylinder, tumbling flights between said first andsecond mixing flights, bucket flights forming a portion of one of saidcharging flights and one of said return flights.

4. In a, concrete mixing and transporting machine the combination of anelongated rotatable cylinder having converging ends one of which is openand the other closed, and a plurality of flights mounted within saidcylinder adapted to carry materials from the open end to the closed endof said cylinder and back again in repeated succession, the flow ofmaterial from one end of the cylinder to the other being interruptedonly by partial diversions of the streams of material causing afractional part to reverse its direction of travel and join a differentstream for the purpose of securing a mixture of uniform characteristicsthroughout the mix consisting of a set of charging flights at the openend of said cylinder including one bucket flight for elevating a portionof the charge, a set of mixing flights having the same general directionas do said charging flights, a second set of mixing flights having areverse direction of slope than do said first mentioned mixing flights,a tumbling flight standing substantially parallel to the axis of thecylinder, and return flights opposed to said charging fl ghts anddisposed at the closed end of said cylinder.

5. In combination with a motor truck having a drivers cab, a tiltableframe mounted on the truck, a concrete mixer on the tiltable frame, awater tank and piping therefrom to the mixer and a pump interposed inthe piping all carried on said tiltable frame, transmission foroperating the mixer from the truck power, and a shaft operated by theoperation of the mixer arranged for operating said pump.

6. A transit concrete mixer comprising an auto truck, a voluble mixingshell mounted thereon, means to rotate the shell. from the truck's powerplant, and means actuated by said power plant means for supplying waterto said shell.

7. A transit concrete mixer comprising an auto truck, a voluble mixingshell mounted thereon, means to rotate the shell from the trucks powerplant, and water supply means for said shell including a, pump adaptedto be driven by said power plant.

8. A concrete mixer, means whereby the mixer may be mounted on a motortruck for operation by the power thereof, piping for supplying water tothe mixer, a pump arranged for forcing water through said piping, andmeans for operating the pump by the power of the truck.

9. In combination with a motor truck, a tiltable frame thereon, aconcrete mixer mounted on the frame, power transmission arranged foroperating the mixer from the power of the truck, a water tank carried bythe truck, and a water pump for forcing water from the tank to themixer, said pump carried on the tiltable frame and arranged foroperation from the power of the truck.

10. In combination with a motor truck having a drivers cab, a tiltableframe mounted on the truck, a concrete mixer on the tiltable frame, awater tank and piping therefrom to the mixer d a, pump interposed in thepiping all carried on said tiltable frame, and transmission foroperating the mixer and the pu p from the Power of the truckcontrollable from the driver's cab.

11. In a revolvable cylindrical concrete mixer drum provided with arelatively short cone at one end through which material to be mixed isreceived and discharged, a plurality of blades se-' drum provided with arelatively short cone at one end through which material to be mixed isreceived and discharged, the length of the cylindrical portion of thedrum being substantially greater than the diameter, a plurality ofblades secured to the inner wall of the drum arranged at opposite anglesof inclination for screwing the material back and forth and from end toend in the cylindrical portion of the drum as the same is revolved, andblades in the cone portion of the drum inclined to screw the materialone way only upon one way revolution of the drum.

PORTER W. YE'I'I'.

